Basically a translator vehicle has a different coupler at one end, so it can attach in this case to the Dellner coupler on the Class 397 EMU, so 1 translator vehicle each end of the EMU. The brake pipe for train braking is then continuous throughout the train through the barriers and rear locomotive in this case for added brake force. The brakes may or may not be working on the 397, if not that's when more additional brake force is required.
Some of the ROG operated locomotives have a Dellner coupler and equipment fitted so no need for translator vehicles.